Many types of internal combustion engines, such as those used with tractors, heavy construction equipment, trucks, and the like, have vertically extending exhaust pipes, and protective caps are frequently associated with the vertical exhaust pipe to prevent rain and snow from entering the exhaust pipe, as well as to prevent foreign objects from entering the pipe during periods of non-use of the engine.
One type of protective cap that has been used in the past is a flap which is pivoted to the upper end of the exhaust pipe and is movable under the pressure of the exhaust gas from a closed horizontal position to a pivoted open position.
A second form of protective cap that has been employed in the past includes a flat plate that engages the upper end of the exhaust pipe and moves vertically relative to the pipe under the pressure of the exhaust gas.
Protective caps as used in the past have had certain disadvantages. In some cases the protective cap can only be used on original equipment and cannot be mounted on existing exhaust pipes, while in other cases, substantial modification of the exhaust pipe is required in order to install the protective cap.
A further disadvantage of the protective cap as used in the past has been the tendency of the cap to rattle or vibrate when the cap is in the raised position during the operation of the engine, and in some cases strong winds have opened the cap during periods of non-operation of the engine, permitting rain and snow to enter the exhaust pipe.